Toast the pecans by spreading them on a baking sheet and baking at 350°F for 8-10 minutes until fragrant and slightly darkened. Watch carefully to prevent burning. Set aside to cool completely.
Brown the butter in a light-colored saucepan over medium heat, stirring occasionally. It will foam, then the milk solids will turn golden brown and smell nutty (about 5-7 minutes). Immediately transfer to a heat-proof bowl and cool for 20 minutes.
Preheat your oven to 350°F and line two baking sheets with parchment paper.
Combine the cooled brown butter and both sugars in a large mixing bowl. Beat with an electric mixer for 2-3 minutes until light and fluffy.
Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract.
In a separate bowl, whisk together the flour, baking soda, salt, and cinnamon (if using).
Gradually add the dry ingredients to the butter mixture, mixing on low speed just until combined. Don’t overmix.
Fold in the toasted pecans by hand using a spatula until evenly distributed throughout the dough.
Scoop dough using a 2-tablespoon cookie scoop and place 2 inches apart on prepared baking sheets.
Bake for 10-12 minutes until the edges are golden but the centers still look slightly underdone. They’ll continue cooking on the hot baking sheet.
Allow cookies to cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.